Edit: (4th Dec. 2016)
The humans unintentionally inhaled as little as possible.
Superman intentionally inhaled millions/billions of times more. (The entire cloud that comes out of the huge orb.)
The famous sneeze that destroyed a solar system.
I try not to get involved in stuff like this. I enjoy reading Superman comics as I do other powerful heroes. But I saw the scan for the first time today and couldn't help but comment on it.
The entire page is drawn and written to emphasize the sneeze happens to the extent it does because of "5th dimensional magic" powder. It couldn't be more literal and blatant.
Superman looks down and see's people unintentionally inhaling a cloud of something.
Mr Mxyzptlk says (quote)
" Tee-hee! I did it all with my 5th dimensional magic, super-sap! "
Superman thinks (quote)
" I'm swiftly inhaling all the sneezing powder in through my nostrils! "
Superman intentionally inhales the entire cloud, thousands/millions of times more than any individual human did.
" Okay, Super-ham! You asked for it! You're invulnerable to everything - - Except my magical powers"
Superman flies off and sneezes.
How much clearer could it be? How many more times did they have to mention magic?
Everything about this is deliberately and literally saying the sneeze happened to the extent it did because of the massive amount of magical powder Mr Mxyzptlk tricked Superman into inhaling.
If this was a moderate sized "feat" Superman "vs fans" would admit in a second it was because of the (quote) "5th dimensional magic" and move on to a feat without an outside force. But because it is Superman's biggest destruction feat this one page being misinterpreted (perhaps deliberately so) stops many “vs” conversations.
No matter how tight you have your blinders on there’s absolutely no way to deny this has far too much outside influence to be considered an actual feat.